Pre-alloyed nickel-free silicon-free minimal oxide low alloy iron powder

ABSTRACT

A pre-alloyed nickel-free silicon-free low-alloy iron powder with minimal oxide content yet possessing good hardenability and good mechanical and metallurgical properties for the production of sintered powdered metal articles is prepared by alloying iron with approximately one-half of one per cent molybdenum and approximately one-half of one per cent of manganese. Any desired carbon content is obtained either by combining carbon with the molten alloy prior to atomization or by adding graphite thereafter to the pre-alloyed powder by blending prior to compacting. The detrimental oxides normally created during the production of these compactible metal powders by the high temperature atomization of the molten metal from which they are formed are reduced to negligible amounts having harmless effects by passing the pre-alloyed powder through a sintering furnace containing a reducing atmosphere, such as a hydrogen or dissociated ammonia gas atmosphere. The sintered powdered alloy cake thus produced is then pulverized to form the alloy powder of the present invention. Comparative tests described, and their results set forth herein, show that the present invention alloy powder, although omitting the nickel content previously thought necessary, nevertheless retains the functions of, and compares favorably in performance with the prior nickel-content iron alloy powders.

United States Patent [191 l 1111 3,798,022

LeBrasse et al. Mar. 19, 1974 PRE-ALLOYED NICKEL-FREE [57] ABSTRACT SILICON-FREE MINIMAL OXIDE LOW A pre-alloyed nickel-free silicon-free low-alloy iron ALLOY IRON POWDER powder with minimal oxide content yet possessing [75] Inventors; G d J, L m- A A b good hardenability and good mechanical and metallur- B if smh i Grosse p i gical properties for the production of sintered powwoods, b f Mi dered meta] articles is prepared by alloying iron with approximately one-half of one per cent molybdenum [73] Asslgnee: Federal'Mogul corpomuon and approximately one-half of one per cent of mangasouthfield' nese. Any desired carbon content is obtained either by 22 Filed; 20 1972 combining carbon with the molten alloy prior to atomization or by adding graphite thereafter to the pre- [211 Appl' 235390 alloyed powder by blending prior to compacting. The

Related s Application Dam detrimental oxides normally created during the pro- [62] Division of 581. No. 115.994, Feb. 17. 1971, Pat. No, dPction of these pa ihle metal powders by the 3576.103. high temperature atom1zat1on of the molten metal from which they are formed are reduced to negligible 52 US. Cl. 75/05 BA amounts having harmless effects by Passing the P 51 Int. Cl 132219/00 alloyed Powder through a sintering furnace Containing [58] Field of Search 75/0.5 BA, 123 J, 123 N a reducing atmspherei Such as a hydrogen or dissociated ammonia gas atmosphere. The sintered powdered [56] References Cited alloy cake thus produced is then pulverized to form UNITED STATES PATENTS the alloy powder of the present invention. Comparative tests described, and their results set forth herein,

3,687,654 8/1972 Huseby 75/05 BA Show that the present invention alloy powder.

3 597 188 8/1971 Neumann 75/O.5 BA 9 thou h om1tt1n the nickel content rev1ousl thou ht s'szsosl (M970 Huseby et 75/0'5 BA nece sa nevgrtheless retains the function of a nd 3.424.572 H1969 Parikh 75/05 BA f bl f h h 2,799,570 7/1957 Reed et al. 75/05 BA CPmPaWS avofa Y Per Oman t e nickel-content iron alloy powders. FOREIGN PATENTS OR APPLICATIONS Great Britain 2 Claims Drawing Figures Primary E.raminer-W. W. Stallard Attorney. Agent, or Firm-Willis Bugbee THEREBY REDUCING OXIDES TO ALLOY AND msums THEREBY SINTERING EXPELLING NICKEL-FREE TOWING BTAININ PRE-ALLOYED OTHER REACTION Fv a" m "one" PRE 'ALLOYED OXIDE-CONTAINING PRODUCTS "no Rim/m OXIDE-CONTAINING Fe/Mn/Mc AS snsss RIM" [Mo ALL Fe/Mn/m POWDER IN ALLOY POWDER REDUCING ATMOSPHERE THEREBY OBTAINING SUBSTANTIALLY OXIDE'FREE PRE-ALLOYED SINTERED POWDERED Fe/ Mel/Mo ALLOY CAKE PULVERIZING BLENDING THEREBY SUBSTAIITIALLY POWDERED oanmms OXIDE FREE CARBON NICKEL-FREE PRE'M-WYED SUBSTANTIALLY SINTERED SUBSTANTIALLY oxm FREE Pow/cease FREE Fe /Mn lMo/C FQ/Nn/Mo v PRE-ALLOYED PQWDER ALLoY CAKE rem mo POWDER 3LT98L022 PATENTEUMAR I 9 r974 saw 01 or m PATENTEDHAR 1 9 m4 3798.022

sum as ur 1o PATENTED MAR 1 9 I974 SHEET 08 0F 10 PATENTEU MAR 1 9 1974 SHEET 09 0F 10 FIG. l6

PATENTED MAR 1 9 I974 SHEET 10 HF 10 PRE-ALLOYED NICKEL-FREE SILICON-FREE MINIMAL OXIDE LOW ALLOY IRON POWDER This is a division of our co-pending application, Ser. No. ll5,994, filed Feb. I7, 1971, for Pre-Alloyed Nickel-Free Silicon-Free Minimal-Oxide Low-Alloy Iron Powder and Method of Making the Same. now US. Pat. No. 3,676,103, issued July I1. 1972.

BACKGROUND AND SUMMARY OF INVENTION In the powder metallurgy industry a low-alloy" iron powder is one in which the alloy ingredients total less than 3 per cent. Prior low-alloy powders having good hardenability and good mechanical properties have hitherto been prepared by blending or alloying manganese, nickel and molybdenum powders in amounts of approximately one-half of one per cent each, the remainder being iron containing the desired amount of carbon. Nickel powder, however, is very expensive and in short supply, and the temporary cutting off of the supply of nickel, as by labor strikes, has hitherto created havoc in the powder metallurgy industry. The manganese ingredient is very desirable for facilitating heat treating because it renders hardening easier. Manganese, however, possesses the very serious disadvantage of easily oxidizing, which has hitherto prevented it from being supplied to makers of powdered metal parts because of the fact that such oxidation impregnates such parts with particles of oxides of manganese. Iron, molybdenum and silicon also form oxides when melted and atomized. These oxides contaminate the alloy by acting as foreign bodies, which in turn create an irregular metallurgical microstructure. The presence of such oxides in such a sintered powdered metal alloy makes it hard to handle, and greatly reduces the elongation, impact and compressibility properties. Silicon has hitherto been frequently added to the molten alloy to increase the fluidity of the alloy so as to improve its atomization characteristics, but silicon when oxidized forms acid insolubles and, therefore, undesirable silica. These undesired oxides and foreign matter are termed dirt" in the powdered metal industry.

Thus the well-known prior silicon-content S.A.E. 4400 iron alloy powder which the iron alloy powder of the present invention is intended to replace, has the following composition:

manganese 0.45 100.65 K

with the remainder iron, silicon 0.20 to 0.35 i

plus carbon to suit. molybdenum 0.45 to 0.60 X

Furthermore, the also well-known prior nickel-content S.A.E. 4600 iron alloy powder which the alloy powder of the present invention is likewise intended to replace, has the following nominal composition:

manganese 0.20

with the remainder iron. plus nickel L75 X carbon to suit. molybdenum The pre-alloyed nickel-free silicon-free minimaloxide low-alloy iron powder of the present invention,

containing manganese alloyed with molybdenum in amounts of one-half per cent each, with iron and carbon to give the desired composition, and prepared as set forth below under deoxidizing conditions, eliminates the above-mentioned short-comings of prior low-alloy iron powders without the use of either nickel or silicon, and reduces the detrimental oxides to a minimum while achieving a superior metallurgical micro-structure demonstrated by photomicrographs herein comparing it with prior art alloys. Extensive tests, described below and with the results thereof either set forth graphically in the drawings hereof or in tabular form below, show that the pre-alloyed nickel-free silicon-free minimaloxide low-alloy iron powder A of the present invention, made in accordance with the method described below of the present invention, when tested in comparison with much more expensive prior nickel-content iron alloys, exhibit properties which for the most part equal and in some cases surpass the similar properties of such prior nickel-content iron alloys. In other words, the nickel-free, silicon-free iron alloy powder of the present invention, although omitting the nickel ingredient previously considered necessary for imparting satisfactory physical and chemical properties to such iron alloy powders, nevertheless retains such properties to such a satisfactory extent that it may be successfully substituted for the prior nickel-content alloy powders for most uses.

In the drawings, in which the present invention iron alloy powder is designated A and typical prior commercial nickel-content iron alloy powders are designated B," D" and 13" respectively for comparative purposes,

FIG. 1 is a flow sheet showing diagrammatically the steps in the method of making the nickel-free siliconfree minimal-oxide pre-alloyed iron powder A" of the present invention;

FIG. 2 is a graph showing .lominy hardness test curves of the nickel-free silicon-free minimal-oxide pre-alloyed iron powder A" of the present invention;

FIG. 3 is a graph showing Jominy hardness test curves of prior nickel-content alloy powder B;"

FIG. 4 is a graph showing .lominy hardness test curves of prior nickel-content and copper-content alloy powder C;"

FIG. 5 is a graph showing .lominy hardness test curves of prior nickel-content alloy powder D;"

FIG. 6 is a graph showing .lominy hardness test curves of prior nickel-content alloy powder E;"

FIG. 7 is a graph showing comparative compressibility curves of the alloy powder A of the present invention and of prior alloy powders B, C," D and FIG. 8 is a graph showing comparative tensile test properties of the low-carbon iron alloy powder A" of the present invention and prior low-carbon alloy powders D" and E;"

FIG. 9 is a graph showing comparative tensile test properties of the high-carbon iron alloy powder A" of the present invention and prior high-carbon alloy powders D" and E;"

FIG. 10 is a graph showing comparative Charpy impact test properties of the low-carbon iron alloy powder A" of the present invention, and prior low-carbon alloy powders B, C, D," and E;

FIG. I1 is a graph showing comparative Charpy impact test properties of high-carbon iron alloy powder A of the present invention, and prior high-carbon alloy powders C, D" and E;"

FIG. 12 is a photomicrograph of a low-carbon heattreated Nital-etched sintered powdered metal sample made from the nickel-free silicon-free minimaloxide prealloyed iron powder A of the present invention, under 300 diameter magnification;

FIG. 13 is a photomicrograph of a low-carbon heattreated similarly etched sintered powdered metal sample made from prior nickel-content iron alloy powder also under 300 diameter magnification;

FIG. 14 is a photomicrograph of a low-carbon heattreated similarly etched sintered powdered metal sample made from prior nickel-content iron alloy powder C. also under 300 diameter magnification;

FIG. 15 is a photomicrograph of a low-carbon heattreated similarly etched sintered powdered metal sample made from prior nickel-content iron alloy powder also under 300 diameter magnification; and

FIG. 16 is a photomicrograph of a low-carbon heattreated similarly etched sintered powdered metal sample made from prior nickel-content iron alloy powder E," also under 300 diameter magnification.

METHOD OF PREPARING LOW-ALLOY NICKEL-FREE IRON POWDER OF PRESENT INVENTION In preparing the pre-alloyed nickel-free silicon-free minimal-oxide low-alloy iron powder of the present invention (FIG. 1), iron is melted in a suitable furnace. While the iron is in a molten state, manganese metal and molybdenum metal are added to the molten iron, which now contains the proper quantities of manganese and molybdenum. This alloy in the molten state is then discharged through a suitable nozzle while subjected to the action of high pressure fluid such as pressurized steam or other suitable pressurized fluid which converts the molten metal into a pre-alloyed metal powder. Each particle of this pre-alloyed metal powder contains the same ratio of iron, manganese and molybdenum. Such metal atomizing nozzles are shown, for example, in the Robert L. Probst et al U.S. Pat. Nos. 2,968,062 of Ian. I7, I96] and 3,253,783 of May 3], 1966, and the procedure is set forth in an article thereon in the journal Precision Metal Molding for February 1959. This pre-alloyed powder is passed through a suitable furnace containing a reducing atmosphere such as hydrogen or dissociated ammonia, which removes objectionable oxides.

The pre-alloyed iron powder of the present invention, in response to the heat of the sintering temperature, emerges from the furnace in the form ofa sintered powdered alloy cake, the particles of which are tenaciously joined to one another. The sintering temperature employed in the deoxidation procedure just mentioned is in the neighborhood of 1,800 F. with an acceptable range of l,400 to 2,000 F.

It will be understood that during the reduction step after atomization of the molten alloy, the alloy oxides are reduced to their respective metals while the other reaction products are expelled in gaseous form. Thus where the atmosphere is hydrogen, the other reaction product is water vapor.

The sintered powdered iron alloy cake thus produced is then allowed to cool, whereupon it is then pulverized,

as by grinding, which reduces it to fine particles which, unlike the approximately spherical particles produced during atomization, are of non-spherical configuration. As a result, when the nickel-free silicon-free minimaloxide pre-alloyed iron powder of the present invention is compacted into briquettes in a conventional briquetting press, the particles interlock with one another and because of their irregular shape adhere tenaciously to one another, with the result that the briquettes and the sintered powdered metal alloy articles made therefrom are found by comparative tests to possess mechanical properties which are in most cases equal or superior to those of articles made from prior nickel-content iron alloy powders.

COMPARATIVE TESTS OF PRESENT PRE-ALLOYED NICKEL-FREE LOW-ALLOY IRON POWDER WITH PRIOR NICKEL-CONTENT PRE-ALLOYED IRON POWDERS For comparative purposes, sintered powdered test samples of the pre-alloyed nickel-free low-alloy iron powder *A" of the present invention and of prior commercial nickel-content low-alloy iron powders B, C, D'- and E" were made use of. The exact chemical composition of the samples tested was determined by chemical analysis and is shown in Table I below:

TABLE I Chemical Composition Material Hi-C Lo-C Mn Ni Mo Present 0.59 0.28 0.48 0.59 invention nickel-free iron alloy powder "A" Prior 0.63 0.29 0.13 1.69 0.45 0.l3

powder D" The five iron alloy powders were then tested for apparent density and relative rates of flow, with the results shown in Table II below:

TABLE II Apparent Density and Flow Rate Material Apparent Density b/cc Flow Rate, Sec.

Present invention 2.53 34 nickel-free iron alloy powder A" Prior nickel-content 2.94 27 iron alloy powder TABLE Il-Continued Apparent Density and Flow Rate Material Apparent Density b/cc Flow Rate, Sec.

Prior nickel-content 2.79 34 iron alloy powder Prior nickel-content 3.22 24 iron alloy powder Prior nickel-content 2.77 34 iron alloy powder The five iron alloy powders were then formed into similar briquettes in the form of MPIF Standard -63 flat tensile bars, the compacting being carried out at 30 tons per square inch. Comparative compressibility tests of the five iron alloy powders A," B, C, D" and E" were also made and the results thereof are shown in FIG. 7.

Samples of each of the five iron alloy powders in the form of green briquettes were tested as regards their green strength, at a compacting pressure of 32 tons per square inch. The comparative results are shown in Table III below, based upon an average of three sam-.

ples each being tested.

TABLE III Green Strength (At 32 T8! Compacting Pressure) Material Green Strentgh. psi

Present invention nickel-free iron alloy powder A 1764 Prior nickel-content iron alloy powder I535 Prior nickel-content iron ulloy powder 2100 Prior nickel-content iron alloy powder 8" 1218 Prior nickel-content iron alloy powder D 1855 Two sets of the above identified flat tensile bars com pacted at 30 tons per square inch each were sintered under the typical conditions shown in Table IV below. The bars of alloys .A and E" were sintered together, as shown in the upper portion of Table IV. Prior alloy powders B," C and D", which arrived later in the test program were sintered as shown in the middle and lower portions of Table IV, under conditions as similar as possible to those of alloy powders A" and E."

TABLE IV Sintering Conditions for Present invention Alloy Powder A" and for Prior Alloy Powder E" Pre-hcat zone temp. l500 F.

Hot zone I 2050 F,

Hot zone 2 2050" F.

Atmosphere Endothermic gas Dew Point (hot zone) +40l42 F.

Speed setting 8 Sintering Conditions for Prior Alloy Powders 8" and LACI Pre-heat zone temp. l500 F.

Hot zone l 2050 F.

Hot zone 2 2050 F.

Atmosphere Endothermic gas Dew Point (hot zone) +37l39 F.

Speed 2 min./ftv

Sintering Conditions for Prior Alloy Powder D Pre heat zone temp 1200 F. Hot zone I 1900 F.

Hot zone 2 2040" F.

Atmosphere Exo/endo gas Dew Point (generator) 32 F.

Speed 2.5 min./ft.

One set of the bars was reserved for testing in the low density or as sintered" condition, while the bars of the other set were heat-treated together. The heat treatment data for the low-density samples are given below in Table V.

TABLE V Heat Treatment, Low Density Samples Temperature I550" Fv Time 45 min. Atmosphere Endothermic gas Dew point +45l50 F. Quench Warm oil Temper 300 F. 1 hour Both sets of bars were surface-fround to insure flatness, and then were tension-tested. The comparative results of these tension tests of the low-carbon specimens are listed in Table VI entitled Low Density Evaluationz" TABLE VI Low Density Evaluation NOTE: All of the above powders were prepared with 0.70% graphite. Prior nickelcontent alloys "8 and D were not available for this testv ln orde r to evaluate the five iron alloy powders comparatively at high density, green bars weighing 218 grams and approximately 0.650 inches wide by 1.0

TabIe VTI GWIinued i i B) High carbon group Tem erature l550 F. inches high by 3.0 inches long were compacted from 1 how each powder at 30 tons per square inch pressure. The g ph Eggs 3 552 gas CW Oll'l bars of each alloy powder were made in both low carouenzh warm 0 bon (0.3 percent graphite) and high carbon (0.7 per- Temper for 1% hflurs cent graphite) mixes to simulate carburizing and $235 for M hours through-hardening type materials. The bars were then +o00 F. for i hour sintered as shown in Table IV above. the bars ofcertain of the prior test materials being sintered separately beone Set of bars from each group of forged bars was Cause as above the Powders of whch they were also machined into Jominy hardenability test samples. made had amved later on m h program These Jominy test samples were furnace-heated and q- These bars were h sufficen'dy heated and forged uenched in a new Jominy unit in accordance with SAE test by bemg Struck a Smgle blow at a Standard 1-4060. Rockwell hardness readings were suitable forging pressure. The density of these test bars taken at 1/16 of an inch intervals in the customary ranged forgmg from percent theorelcal for manner prescribed for .lominy hardenability tests. The the more difficult forging materials to 99.6 percent theresults for the present invention alloy are shown otretictal for the more easily fogged matterials. Thel bars in FIG. 2 whereas the results for prior alloys ti a ter orging were then passe throug a norma izing and are Shown in FIGS 3 4 5 and 6 respec chamber filled with an atmosphere of commerical entively dothermic gas, which is a product obtained by cracking Certain of these forged bars were also used to natural mcthzine g g g g a duce Charpy Vee-notch specimens in accordance with manly 0750mm by me es y i A.S.T.M. specifications E-23. After rough machining, f rough'wmed to produce 4 mun tens e these bars accompanied the above-described tensile grmd stock allowance "catmem of these test bar specimens through heat treatment according to rough bars '0 then perform! Separaely the the conditions set forth in Table VII mentioned above. carbon and high-carbon sets under the heat-treatment 7 conditions set forth in Table VII. Final grinding and Charpy impact testing was then per- TABLE v" 0 formed. The results of the comparative tensile tests for the low-carbon specimens are shown in FIG. 8 whereas Hem Treatment High Densiy Samples those for the high-carbon specimens are shown in FIG. A) Low carbon group i 9. The impact test data for the low-carbon specimens so are shown in FIG. 10 whereas those of the high-carbon Ifgf JQ specimens are shown in FIG. 11. The comparative re- Atmosphere Eridothcrmic gas sults of the various tests of the high-density specimens Dew point +60 F. Quench warm on are listed in Table VIII both for low carbon and high Temper 300 F. 1% hours carbon SPCCImCIISI TABLE VIII High Density Evaluation Tens. Hard- Charpy Hard- Str. ness impact. ness Car- Material psi Elong. Rc ft/lb Rc bon l. LOW CARBON (average of 3 samples each) Present invention nickel-free iron alloy m" 222,900 7.0 -50 9.2 49-50 0.28

Prior nickel-conmu iron alloy E 235500 8.0 48-50 7.6 47-49 0.29

Prior nickel-content iron alloy C 229,300 3.0 46-48 3.5 49-50 0.32

Prior nickel-conlent iron alloy "B" 225.400 4.5 47-50 5.9 47-48 0.32

Prior nickel-content iron alloy "D" 218.200 5.0 4445 5.9 4445 0.26

2. HIGH CARBON (average of 7 samples each) Present invention nickel-free iron 260.400 4.2 4940" 2.8 -62 0.59

Prior Nickel content iron alloy E" 253.800 5.0 48-49 3.3 58-61 0,63

Prior nickel-com tent iron alloy "c" 223.600 i.2 48-50 2.3 53- 60 0.66

High'Dcnsity Evaluation Tens. Hard- Charpy Hard- 7r Str ness impact. ness Car- Material psi Elong. Rc ft/lb Rc hon Prior nickcl-cont tent iron alloy "B" 264.700 1.5 49-51 1.8 6l-63 0.72

Prior nickel-content iron alloy D" 254.400 2.2 47-49 L8 59-60 0.61

' Hardness and pro erties after 300' F. temper Hardness and properties after 600' F. temper NOTE: Figures shown are average of all specimens tested.

The specimens or samples which were left from the SUMMARY OF TEST FINDINGS w th us d f0 mi r -e amination for ensue tests T a r t cleanliness The comparative tests of specimens made from the t e r u e f c can b l [X nickel-free silicon-free minimal-oxide pre-alloyed tron ow in a e exammation r Se or c powder A with those of the nickel-content prior tron TABLE [X alloy powders B," C," D" and E" support the following conclusions: 1. All things considered, the pre-alloyed nickel-free- Microexaminatton Prepared samples from each group of test specimens were examined sfllcon'ffee mlplmal oxlde lowjalloy powder of the with it.- following observations 2 5 present invention shares the highest rating, by compari- UNETCHID EXAMINAHON mrclcmlmsl son, with the prior nickel-content iron alloy powder E," with the result that the iron alloy powder of the Present invention nickelfree Contains a fair amount of oxides or present i ti ld b b tit t d i li ti iron alloy "A" non-metallics which now use the prior nickel-content Iron alloy pow- Prior nickel-content iron alloy Containsa fair amountoflarge dark der E,H not only 215 to conventional density Sil'llfil'fid gray particles Prior nickel-content iron alloy Very dirty. large amount of both fine and coarse non-mctallics and oxidcs Appears to contain fincgscattercd silicate-type inclusions Prior nickel-content iron alloy Moderate amount of medium size Prior nickel-content iron allo dark gray non-metullics TABLE X Microexamination ETCHED EXAMINATION (for microstructure) Present invention nickel-free Good transformed structure iron alloy "A" Prior nickel-content iron alloy u Ver uniform good structure Mixture of martensite and Prior nickel-content iron alloy nickel'rich areas Good structure with some Prior nickel-content iron alloy transformation product Martensite structure plus scattered nickel-rich areas and transformation product Prior nickel-content iron alloy powdered metal parts but also as to subsequently forged high-density sintered powdered metal parts.

2. As regards compressibility, flow rate and green strength. the nickel-free iron alloy powder A" of the present inventign compares favorably with the four prior nickel-content iron alloy powders.

3. For regularity of microstructure, the nickel-free iron alloy powder .A" of the present invention (FIG. 12) compares favorably with the prior nickel-content iron-alloy powder E (FIG. 16) and is definitely superior in this respect to the other prior nickel-content iron-alloy powders B," C" and D" (FIGS. 13, 14 and 15).

4. As regards hardenability, the Jominy hardness curves of FIGS. 2 to 6 inclusive show that the nickelfree iron alloy powder A" of the present invention is superior to prior nickel-content iron alloy powder B. compares favorably with prior nickel-content iron alloy powders D" and E" and is surpassed over a considerable range of distances from the quenched end by prior nickel-content alloy C."

5. For tensile strength in the low-carbon range (FIG. 8), the present invention nickel-free iron alloy powder A is exceeded only by prior nickel-content iron alloy powders (1" and E and is superior to prior nickelcontent alloy powders B and D."

6. For tensile strength in the high-carbon range (FIG. 9) the present invention nickel-free iron alloy powder A is exceeded only by prior nickel-content alloy B and is superior to prior nickel-content iron alloy powders D" and 7. As regards impact performance in the low-carbon range (FIG. 10). the nickel-free iron alloy powder A of the present invention is markedly superior to all four of the prior nickel-content iron alloy powders D" and whereas in the high' carbon range (FIG. 11), the present nickel-free iron alloy powder .A" is surpassed only by the prior nickel-content alloy powder 15" and is superior to the prior nickel-content iron alloy powders B, C" and D.

CONCLUSION I claim:

1. A pre-alloyed nickel-free silicon-free minimaloxide low-alloy iron powder adapted for the production of high-strength sintered powdered iron alloy articles said pre-alloyed iron powder being free from nickel and silicon and consisting essentially of iron from 97.0 to 99.0 percent,

manganese from 0.25 to 1.50 percent,

molybdenum from 0.25 to L00 percent, and

metallic oxide less than 0.20 percent.

2. A pre-alloyed nickel-free silicon-free minimaloxide low-alloy iron powder, according to claim 1, wherein the particles of said pre-alloyed powder are preponderantly of irregularly shaped non-spherical configuration. 

2. A pre-alloyed nickel-free silicon-free minimal-oxide low-alloy iron powder, according to claim 1, wherein the particles of said pre-alloyed powder are preponderantly of irregularly shaped non-spherical configuration. 